The new generation mobile communication system is required to have multimedia data transmission capabilities of high rate, high spectral efficiency and high capacity. Serious frequency-selective fading will occur in high speed data transmission in the wireless environment, while the Orthogonal Frequency Division Multiplexing (OFDM) technology stands out due to its prominent advantages and becomes the focus of attention.
The OFDM is a multi-carrier transmission technology in which subcarriers are mutually orthogonal. The OFDM divides one wider transmission bandwidth into mutually orthogonal multiple subcarriers for parallel transmission of data. The OFDM has advantages, such as high frequency spectrum utilization, anti-multipath fading, simple implementation of the Multiple-Input Multiple-Output (MIMO) technology and so on. However, because the OFDM technology requires the characteristic of mutual orthogonality between the subcarriers, it is very sensitive to the frequency offset.
In the OFDM technology, the existence of the time offset will cause inter-symbol interference (ISI), thereby influencing on the precision of frequency offset estimation. Although the influence of the time offset on the OFDM is reduced to some extent due to the introduction of a concept of cyclic prefix into the OFDM, it is required to ensure that the time offset cannot be too big; otherwise, the data will be seriously disturbed, causing the loss of performance.
It can be seen that the synchronization issue is one of core issues of the OFDM technology. A variety of synchronous solutions have been proposed by a lot of communication engineers for decades. If a frequency offset estimation method for continuous pilot symbols continues to be used for estimating a frequency offset for comb pilot symbols, the loss of estimation precision will be relatively large. However, there is no pertinent literature describing how to estimate a frequency offset by using discontinuously distributed pilot symbols, such as comb-distributed pilot symbols, and ensure that there is no loss with respect to the continuously distributed pilot symbols.